Wheel of Time MUD

Does anyone have any anecdotes or ideas of what limits this?

I was just reading an old email of an alt, who had 391 hps at level 30 and 403hps at level 51, and looking at the average of 20hps for 19 con chars from level 30 to 50, and am wondering how unlikely that is?

Of specific note I distinctly remember I had 'just' started my whole nibbling thing when leveling that character, and I think they were at like 398 at level 35,..then just didn't seem to gain any more for like 15 levels..

I know a friend anecdotally found that the mentals of their statters went up dramatically when fed (or hps or something, I never really saw details).

Just having a bit of a play 21d3-21 averages 21hps with a standard deviation of 3.74
So 2 standard deviations would be 14-28hps
To get these hps had to be out by more than 3 standard deviations - or to put it otherwise there was a 99.5% chance of getting 403hps or better...
This.. just seems outside of the norm enough that I'd be really keen to query what people know.

If I remember right and they were 398hps at level 35 - then the probably of rolling more than 403hps was around 99.99%
(Average hps from here would have been 414; 408-420 would be 2 standard deviations either way)

Am I misunderstanding something about math?